Ciprofloxacin, marketed as Cipro, targets bacterial DNA gyrase and topoisomerase IV. These enzymes are crucial for bacterial DNA replication, transcription, and repair.
Inhibition of DNA Gyrase and Topoisomerase IV
Ciprofloxacin binds to these enzymes, preventing them from properly functioning. This blockage halts DNA replication, effectively stopping bacterial growth and leading to bacterial death. The drug’s potency stems from its selective action; it primarily affects bacterial enzymes, leaving human DNA largely unaffected.
Specificity and Bacterial Targets
The precise mechanism involves the formation of a ternary complex: Ciprofloxacin binds to the enzyme-DNA complex. This complex then inhibits the enzyme’s ability to relax supercoiled DNA. Consequently, DNA replication and cell division are disrupted.
| DNA Gyrase | Introduces negative supercoils into DNA | Inhibits DNA unwinding, blocking replication |
| Topoisomerase IV | Separates replicated DNA during cell division | Prevents DNA separation, leading to cell death |
Gram-Negative vs. Gram-Positive Bacteria
Ciprofloxacin’s effectiveness varies between Gram-negative and Gram-positive bacteria. Gram-negative bacteria, possessing an outer membrane, generally demonstrate higher resistance to Ciprofloxacin than Gram-positive bacteria. This difference reflects varying degrees of drug penetration into the bacterial cells.
